This invention relates to a process for separating CO or CO+CO.sub.2 from mixture comprising N.sub.2 and CO, or N.sub.2, CO.sub.2 and CO by pressure swing adsorption (PSA), and particularly relates to a process for removing a nitrogen gas from exhaust gas of blast furnace or converter furnace by PSA.
In general, exhaust gases from blast furnace and converter furnace comprise the following components:
______________________________________ CO H.sub.2 CO.sub.2 N.sub.2 O.sub.2 ______________________________________ Exhaust gas from blast furnace 23.0 3.0 20.0 54.0 0 Exhaust gas from converter 66.0 2.0 16.0 15.9 0.1 furnace (percent by volume) ______________________________________
Since these exhaust gases contain a relatively considerable amount of carbon monoxide, these gases were used as a reducing agent or a combustion gas for blast furnace or converter furnace by circulating these gases into blast furnace or converter furnace.
However, these gases contain large amount of nitrogen with carbon monoxide. When these gases are used as a combustion gas in these furnace, nitrogen suppresses the combustion of carbon monoxide in these furnace. Therefore, when these exhaust gases are used as a combustion gas, it is desirable to remove nitrogen from these gases.
When gaseous mixture containing two or more gaseous components passes through a column containing an adsorbent, the adsorbent exhibits selective adsorption property to specific component in the mixture. Therefore, separation of one component from a mixture containing two or more components is made possible by using an adsorbent by PSA. There are many patents and patent applications relating to processes for separating poorly adsorbable component from a poorly adsorbable component and easily adsorbable component-containing mixture by PSA. For example, oxygen has been separated from air containing oxygen (poorly adsorbable component) and nitrogen (easily adsorbable component) by PSA in the prior.
However, adsorbents being capable of selectively adsorbing nitrogen from a mixture of nitrogen and carbon monoxide have not beeh prepared. Therefore, process for separating easily adsorbable component from a mixture of easily adsorbable component and poorly adsorbable component by PSA have not been developed. For example, it has been thought in the prior art that it is impossible to separate CO or CO+CO.sub.2 from exhaust gases of blast furnace or converter furnace.